Also, using a PiCap, it seems to work if I exceed the 1000 pixel limit imposed by the UI. Limited testing with 1440 pixels seems to work fine. Can anybody confirm the real limits?

Depends on the sequence timing.... If you use 25ms sequences, the limit is really about 800. If you exceed 800 pixels with 25ms timing, I'm not sure what will happen. The F8-* capes will start dropping frames. Not sue what the Pi's would do.

Thanks for the response. I can confirm that 1440 WS2812B pixel matrix does work at 50ms. I thought before I split that into two channels that I would try it at 25ms. Over the course of 3 minutes, I maybe saw one glitch. It performed better than I expected perhaps because it of the short inter-led distance. Or perhaps I'm not seeing it. What would you expect a failure to look like? Does the whole panel miss a frame or just the first or last pixels? When you miss a frame, would you expect it to be black or the previous value? Thanks again for sharing your experience.

Thanks for the response. I can confirm that 1440 WS2812B pixel matrix does work at 50ms. I thought before I split that into two channels that I would try it at 25ms. Over the course of 3 minutes, I maybe saw one glitch. It performed better than I expected perhaps because it of the short inter-led distance. Or perhaps I'm not seeing it. What would you expect a failure to look like? Does the whole panel miss a frame or just the first or last pixels? When you miss a frame, would you expect it to be black or the previous value? Thanks again for sharing your experience.

Try something like a shimmer that would change the whole string every frame. It would either stay black (only the black frames), white (only the white frames) or some portion of the string would shimmer and the rest static. Also, if the Pi is outputting e1.31 data as well, it MAY cause glitches there as it may be waiting to finish a frame before sending. Not really sure.

That said, you also have to keep in mind that the last pixel on that string is getting it's data almost 40ms after the first pixel. Thus, if it's anywhere close to the first pixel (like zig zagging on a matrix), it may be noticeably lagging compared to the first pixel. Also, if that first pixel dies, that's a lot of pixels that go out.